Maintenance and testing of circuit breakers
During scheduled maintenance, Sin-Ergy inspected, maintained and tested nine low-voltage circuit breakers on an offshore installation in the North Sea. The work combined mechanical maintenance, contact resistance measurements and targeted testing of protection functions. This created an up-to-date record for each circuit breaker covering its technical condition, protection performance and relevant points for future maintenance.
Nine circuit breakers within one maintenance window
The work took place during a scheduled maintenance window on an offshore installation in the North Sea. It covered nine low-voltage circuit breakers: Schneider Electric Masterpact NW and ABB Emax units with rated currents from 800 A to 5000 A and system voltages up to 690 VAC. The different breaker versions and protection units within the same installation meant that each asset required its own assessment. The range of ratings, versions and fitted functions made a single installation-wide conclusion without an asset-level assessment inappropriate. Observations and test results were therefore compiled for each device rather than only as an overall installation result.
Service engineer Mark de Vries carried out the work on site. He holds BOSIET/HUET offshore training for this type of offshore assignment. Preparation focused on completing the work systematically within the available maintenance period while retaining a clear record for each individual circuit breaker.
Mechanical maintenance and electrical checks
Multiple inspection points were assessed systematically for every circuit breaker. The mechanical inspection covered the general condition, main contacts, arc chutes and operating mechanism. Closing and opening coils, auxiliary contacts, wiring and connections were also checked. On withdrawable units, additional attention was given to the racking mechanism, position indication and mechanical and electrical interlocks.
Electrical measurements followed the inspection and maintenance work. Main contact resistance was measured for each phase. Where a protection unit was fitted, the relevant protection functions were checked and tested, including by secondary current injection where applicable. Not every inspection point applied to every breaker version; this remained explicit in each individual assessment. Combining inspection, maintenance and testing shows whether mechanical condition, electrical connections and protection performance collectively support continued operation.
As-found and as-left measurements
On one of the Masterpact circuit breakers, contact resistance before maintenance measured 9, 10 and 9 µΩ across the three phases. After maintenance, values of 6, 6 and 6 µΩ were recorded. The report registers these two sets separately as as found and as left.
This comparison makes both the measured starting point and the condition after maintenance visible. A lower reading alone, however, is not universal proof of a repair or an improvement in quality. Its significance must always be assessed together with the breaker type, measurement method, phase balance, inspection findings and the specifications that apply to the particular device.
Testing the protection functions
The installed protection units included Schneider Electric Micrologic 5.0 A and 5.0 P units and an ABB PR121/P. Depending on the fitted unit and enabled settings, Long Time, Short Time and Instantaneous functions were checked. Protection testing does more than record the settings: the relevant function is tested with an appropriate test current and the actual trip time is registered.
One specific example was the Instantaneous function of the ABB unit. At a test current of 5000 A, a trip time of 0.014 s was measured. Such a value gains meaning within the complete test record: the configured function, applied current, measured trip time and result are all stored against the same asset.
Functionally PASS, with a condition finding
Visible burn marks were found on the arcing contacts of one circuit breaker in the Emergency LV Switchboard. The main contacts were not damaged. The breaker achieved a functional test result of PASS, while its technical condition was assessed as Fair and the observation was recorded separately.
This finding demonstrates why a test result and a condition assessment are both required. A circuit breaker can pass the performed functional tests while still showing visible signs that warrant attention during subsequent inspections or maintenance. Documenting that distinction explicitly keeps both current functionality and condition-based maintenance needs visible.
Condition, lifecycle and the Asset Passport
Technical condition and product lifecycle describe different aspects of an asset. The Schneider Electric circuit breakers carried the lifecycle status Classic in the report, while the ABB Emax was classified as Limited. A device may function technically while belonging to an older or more narrowly supported product generation. Spare-parts availability and manufacturer support may therefore become more restricted over time, which matters when preparing maintenance and future replacement decisions.
The digital Asset Passport brings together measurements, protection settings, inspections, photographs, findings and lifecycle information for each circuit breaker. All nine breakers received a PASS result after the work. Relevant points for attention were recorded separately. The record therefore provides more than a snapshot: it forms a technical basis for future decisions regarding condition, protection performance and maintenance needs.